As a method of desulfurizing exhaust gas, it is known to spray thereon slaked lime in the form of slurry. A conventional apparatus for producing such slaked lime is shown in FIG. 5. This apparatus comprises a vertical shell 1 filled with a pulverizing medium b and a screw shaft 2 extending vertically in the shell 1. A quick lime material s and water are fed into the shell from its top. The material s is pulverized by the friction with the pulverizing medium b and between its own particles while reacting with water such that it turns into slaked lime in the form of slurry.
Since solid impurities such as calcium carbonate and gravel contained in the material are also pulverized into fine particles, the material turns into slaked lime c in the form of slurry containing the above fine particles of impurities and continuously flows out through an outlet 3 at the upper part of the shell 1 into a settling separator 4. It is necessary to pulverize the impurities into fine particles in order to prevent a nozzle from clogging during the above-described spraying. In the drawing, letter P indicates a circulating pump for the settled product.
But during the above-described pulverizing operation, any quick lime material s which is too large to be mixed into a layer of the pulverizing medium b tends to flow directly to the outlet 3 from the inlet. Such unpulverized large-diameter particles are liable to flow through the settling separator 4 and mix into the end product d, thus lowering its commercial value. The larger the ratio of the quick lime material to water, the more remarkable this phenomenon will be. This is because the viscosity of the slurry increases and the separation efficiency by settling decreases as the concentration of the material s grows. Thus, such a conventional apparatus has to be operated under low-concentration conditions. This will lower the production efficiency.
Meanwhile, it is known that a soluble material such as soil stuck to solid pieces such as stones serves to bind them together. If the soluble material melts, the solid pieces will separate. As to the quick lime material s, it contains impurities having a soluble material such as quick lime and the like stuck thereto. If the quick lime and the like melts as a result of reaction, the diameter of its particles will decrease. In other words, the particle diameter of the quick lime material can be reduced and thus it can easily mix into the layer of pulverizing medium b by promoting its reaction and melting.
An object of the present invention is to enhance the reaction and melting of quick lime and to smoothly mix the material to be pulverized into the pulverizing layer by agitating the material in a vertical shell.